How do I make sound and defensible decisions?

You have crossed into real skill: the right tool arrives when the moment calls for it, and you can show your reasoning to anyone who asks. That is what defensible means. Not that you are never wrong, but that your choices come from something you can stand behind. The quiet danger at this level is that frameworks start to feel like proof, and proof can be used to avoid the discomfort of judgment. A model can dress up a decision you already wanted to make. Stay honest about that. The framework serves your thinking; it does not replace the moment where you simply have to choose. Here is a way to keep sharp. On your next big call, write down what would prove you wrong, and revisit it later. Tracking your own misses is what keeps sound decisions from hardening into overconfidence. The best deciders stay a little humble on purpose.